The vast majority of Electrostatic Precipitator (ESP) power supplies in use today operate at a fixed frequency of 60 Hz. In recent years various power supply designs using frequencies in the >10,000 Hz range have been used for ESP’s with the goal of improving ESP field efficiencies. The difference in performance is almost completely due to the low ripple voltage delivered by such power supplies. Redkoh Industries’ high frequency power supply can be operated in a range of 200 Hz to 1000 Hz. At the preferred frequency of 400 Hz the Redkoh system has been demonstrated to achieve ripple reduction to negligible value while avoiding the complexity and reliability problems of higher frequency power supplies.

Precipitator controls and control cabinets are the electrical heart of the precipitator. They control how much power is allowed to flow into the precipitator during various operating conditions. The collection efficiency of the precipitator is directly proportional to the power. This makes the controls a very important component of the precipitator.

Redkoh’s RK2000 TR Control conversion package can be provided to replace existing older controls (both analog and microprocessor) where some of the existing components such as breakers and contactors and control transformers can be reused to save money.

Devices, generically called rappers, are used for cleaning the internals (collecting plates and discharge electrodes) of the precipitator. These rappers are actually single impulse type drop hammers, multi impulse type hammers, electric vibrators, or air solenoids (that control pneumatic vibrators or sonic horns).

The Redkoh CAN-Transceiver is a communication gateway for tying TR controls and Rapper controls directly to a plant DCS or PLC. This allows the electrical operating levels, alarm conditions, and general operating data to be available to the DCS/PLC for report generation or historical logging. If desired, changes to the operating parameters of the controls can also be performed from the DCS/PLC.

A PrecipCommander central control system allows an operator to graphically view the operation of precipitator TR and Rapper controls from a remote location, as well as make changes to the precipitator operating parameters remotely.

Graphic representations of electrical operating levels permits the operator to spot improper precipitator operating conditions before they turn into problems or failures that affect the stack opacity and outlet emissions.

In order to get a secondary voltage signal to a transformer rectifier (TR) control, it is necessary to have a voltage divider resistor connected to the secondary output of a TR. Existing dividers may be located in the oil filled TR tank, or may be located external to the TR in the ground switch housing or pipe and guard (bus duct). TRs that were not manufactured with internal voltage dividers can be retrofitted with external units.

For those instances where a communication link from the TR controls to an existing plant control system (DCS / PLC) is not practical due to limitations of the existing system, a Transducer Box can be supplied to forward electrical levels.

Most precipitator electrical controls manufactured from the 70’s on use silicon controlled rectifiers (SCRs) as the electronic switch that ultimately controls the power to the primary of the TR and in turn to the precipitator. The two most often used types of SCRs are the stud mount and the hockey puck. Both of these types take a significant amount of time to replace if they fail, and both are becoming more expensive to replace.

TR output bushings are typically located on the top of a TR tank (inside an enclosure) or on the side of the TR tank in a bus duct. These output bushings fail from time to time and need to be replaced. Redkoh can supply replacement bushings for this purpose, as well as low voltage bushings typically found in the TR LV junction box.

The current limiting reactor (CLR) is essentially a high current choke that electrically and physically resides in-between the TR control cabinet and the transformer-rectifier tank. The purpose of this choke is to counteract high inrush currents that occur when sparking and arcing take place in the precipitator.

The Transformer-rectifier set, also called a TR or a TR set, converts the low voltage of the plant power system to the high voltage required for precipitator operation. It is referred to as a “set” because the tank contains both the high voltage transformer used to convert relatively low voltage high current AC to high voltage and low current AC, and the full wave diode (rectifier) bridge used to convert the AC to DC for use in the precipitator.